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Frame sizing advice: very confused
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Frame sizing advice: very confused
Postby rogerwilco » Tue May 06, 2014 11:24 am
I'm really confused.
My current ride is an early 90s repco superlite with modern drivetrain (new shimano 105).
Seat tube and top tube are both 56cm CC
90mm quill stem
It feels a little big. Fairly upright riding position, and I have to reach farther than I'd like to get the brake hoods.
Here are my main body measurements:
height: 5'7 (170cm)
actual inseam: 33 inch (crotch to floor)
I know there are many more measurements/fitting required to get a great fit, but for now, I'm just trying to work out whether I should get a new frame, what the right size would be, and whether it's worthwhile doing.
It seems to be that the 'right' frame size for me is probably 53cm CC.
Any and all advice welcome!
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Re: Frame sizing advice: very confused
Postby RonK » Tue May 06, 2014 12:01 pm
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Re: Frame sizing advice: very confused
Postby herzog » Tue May 06, 2014 12:04 pm
53 sounds about right.
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Re: Frame sizing advice: very confused
Postby 39x25 » Tue May 06, 2014 12:29 pm
Depends on the manufacturer... Between 50cm to 54cm tt for someone our height.
I vote new frame time.
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Re: Frame sizing advice: very confused
Postby kb » Tue May 06, 2014 12:49 pm

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Re: Frame sizing advice: very confused
Postby rogerwilco » Tue May 06, 2014 2:25 pm
I'm considering this frame http://www.bicycles.net.au/forums/viewtopic.php?f=25&t=68703
but it is perhaps a little small.
A longer stem could remedy, but I'd rather not... I want to maintain a roughly period correct aesthetic, so I currently have a very nice Nitto pearl quill stem paired with Nitto B105 drop bars. Not the cheapest stem to be replacing...
I guess it's always going to be a bit of a gamble with this kind of build.
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Re: Frame sizing advice: very confused
Postby Nikolai » Tue May 06, 2014 9:11 pm
rogerwilco wrote:but it is perhaps a little small.
If it turns out to be too small, and it probably will, you'll end up with 57 stem spacers and may not be able to move your saddle far enough. Keep calm and keep looking.
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Re: Frame sizing advice: very confused
Postby BriP » Wed May 07, 2014 4:40 am
Sent from my iPhone using Tapatalk
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Re: Frame sizing advice: very confused
Postby Nobody » Wed May 07, 2014 9:13 am
In modern styles you are probably looking at a 51 to 52 seat tube with a corresponding ~53 effective top tube (ETT). But since you are chasing retro, chances are the seat tube angle (STA) is going to be less steep than a modern road bike. The actual body plus arm reach a particular ETT gives is dependent on STA and therefore can't be used in isolation. Better to use the "Reach and Stack" method of measurement including stem height which is explained in the thread below.rogerwilco wrote:Seat tube and top tube are both 56cm CC
90mm quill stem
It feels a little big. Fairly upright riding position, and I have to reach farther than I'd like to get the brake hoods.
Here are my main body measurements:
height: 5'7 (170cm)
actual inseam: 33 inch (crotch to floor)
I know there are many more measurements/fitting required to get a great fit, but for now, I'm just trying to work out whether I should get a new frame, what the right size would be, and whether it's worthwhile doing.
It seems to be that the 'right' frame size for me is probably 53cm CC.
viewtopic.php?f=12&t=67990
As for getting a more accurate guide as to what ETT to chase, try the calculator below. One problem with this calculator is they don't specify the STA, but I believe it may be 73 degrees. Most road bikes in your size would probably be about 74 degrees.
http://www.competitivecyclist.com/Store ... ID=IB12809
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Re: Frame sizing advice: very confused
Postby brentono » Wed May 07, 2014 11:14 am
BriP wrote:yeah i would be suggesting a 50-53cm frame for your height..
Sent from my iPhone using Tapatalk
Exactly my thoughts, and it would depend on the length of cranks, type of shoe and type of seat.
With these square frames, in steel, most of the play is adjusted by seat height and travel, and stem.
(much different than the modern sloping bar frames, which many have not taken into account)
You should, on average, be able to wrap your hand around the amount of seatpost that is out (as a guide)
Some oldskool tips, and maybe I have an interest, but really just tryin' to help. Hope you can work it out.

Maybe I would get somebody to help, and re-check "actual inseam: 33 inch" ... seems high

Cheers

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Re: Frame sizing advice: very confused
Postby metrofarm » Sat Jun 14, 2014 12:09 am
I mention these, and they seem to work for me, because with an old frame, perhaps like the superlite, you might find that you don't get proportional changes in the same way that you do with more modern frames - kind of like you get a 19¦21¦23¦25" range of sizes measured by the seat tube with pretty much the same length top tube. But that's probably only on much older frames. At any rate reach seems most important and I would think that somewhere between a 51 and 54 cm top tube would suit you but more likely towards the 51cm end I would think. I'm about your height (actually 175cm with an inseam of 81 (measured hard up against the bone down there and not where the seam on my jeans happens to be

As has been said above, measure your inseam again (use a thin hard backed book jammed up as high as it'll go standing in your bare feet about 30cm apart) and measure off the book. A friend helps with this obviously, but ... at any rate 33 inches is 83.8 cms and that is quite long relative to a 170cm height. But I'm only thinking a couple of cm's here so its not abnormal.

A final rule of thumb when fitting a bike: the rider shouldn't look like a 'dog rooting a barrel' when pedalling the darn thing. That's technical description and a vivid image! lol
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